This invention relates generally to bus systems and cable connectors for electric power systems, and more particularly to separable insulated loadbreak connector systems for use with modular bus systems.
Electrical power is typically transmitted from substations through cables which interconnect other cables and electrical apparatus in a power distribution network. The cables are typically terminated on bushings that may pass through walls of metal encased equipment such as capacitors, transformers or switchgear.
Separable loadbreak connectors allow connection or disconnection of the cables to the electrical apparatus for service, repair, or expansion of an electrical distribution system. Such connectors typically include a contact tube surrounded by elastomeric insulation and a semiconductive ground shield. Insulated connector probe sleeves are cylindrical with a very small bonding area at the bottom portion of the interface cylinder. A contact piston is located in the contact tube, and a female contact having contact fingers is coupled to the piston. An arc interrupter, gas trap and arc-shield are also mounted to the contact tube. The female contact fingers are matably engaged with an energized male contact of a mating bushing, typically an elbow connector, to connect or disconnect the power cables from the apparatus. The piston is movable within the contact tube to hasten the closure of the male and female contacts and thus extinguish any arc created as they are engaged.
The connectors are coupled to various sized and shaped pieces of bus work to complete the interconnection. Typically the bus work comprises bus bars sized at the site of assembly to account for various configurations of cable risers that carry cables to the electrical switchgear. Such variety of component pieces makes repair or replacement of the components laborious in that each piece is generally custom made and assembled. Insulation is provided between the bus bars and the active switching elements to prevent electrical arcing. There are three common types of insulation typically used in conventional switchgear: oil, sulfur hexafluoride (SF6) gas, and air. Each type of insulation insulates each part of the switchgear from the other parts of the switchgear (bus bar and active switching elements), and from the outer surfaces of the container of the switchgear. However, SF6 gas is difficult to contain, air requirements excessive spacing between energized parts to be an effective insulator, and oil is also difficult to contain and is a fire hazard.
To increase a flashover distance between energized portions and grounded portions of the connector some known connectors are insulated using layers of insulative material covering a length of the energized portion and/or a semi-conductive portion. For example, an insulative layer may be disposed within the recess of the connector along an inner surface. A probe assembly may be contained within the connector and aligned down the axis of the recess. An insulative sheath covers a portion of the exterior of the probe. The insulative sheath surrounding the probe and the insulative layer covering the inner surface of the housing are formed separately and insulative layer is expected to bond securely to insulative sheath at an abutting joint. However, if the abutting joint is not abutted and securely bonded, a gap between the insulative sheath and the insulative layer permits shorting the flashover distance between the energized contact extension and ground potential at an opening end of interface.